The present invention relates generally to a fluid control apparatus and, more particularly, to methods of manufacturing a channeled wall fluid control apparatus.
Thrust nozzles for jet and rocket engines are used for the production of thrust by the combustion of a fuel and an oxidizing agent. As the fuel and oxidizing agent burn, the products of the combustion are expelled from the thrust nozzle, thereby creating thrust. Such engines are usually mounted on aircraft or spacecraft where thrust is used to increase, decrease, or maintain the craft""s velocity in flight.
A by-product of the combustion process is the release of large amounts of heat. To aid in dissipating the heat generated and/or heating of an engine process fluid, the thrust nozzle can be constructed with cooling channels. Heat generated in the thrust nozzle is transferred to the fluid in the cooling channels by conduction, and conveyed away from the thrust nozzle by convection. Cooling channels aid in reducing heat related stresses exerted upon the thrust nozzle, as well as assist in the heating of engine process fluids, thereby increasing engine performance.
One method of manufacturing a channeled wall thrust nozzle was proposed in U.S. Pat. No. 4,942,653, issued to Hawkinson. The disclosed method includes the step of forming a mandrel having a converging-diverging shape. Longitudinally extending slots are then machined within the exterior surface of the mandrel. Channel separator ribs are placed within the longitudinal slots, such that channels are formed between adjacent pairs of separator ribs. The channels are then filled with a removable casting material and the outer surfaces of the separator ribs are machined to have a surface contour conforming to the desired shape of the outer cooling jacket.
An outer shell is then secured around and affixed to the separator ribs. The mandrel is separated and removed from the interior of the thrust nozzle. The exposed inboard surfaces of the separator ribs are machined, followed by the mounting of an inner housing shell to the inner surfaces of the separator ribs. The casting material within the cooling channels is then removed, thereby resulting in a channeled wall thrust nozzle.
Although such a method of forming channeled wall thrust nozzles is effective, it is not without its problems. First, such a method requires precision machining of the mandrel to create a plurality of longitudinal slots to receive the separation ribs. Second, each separation rib must be individually fitted into the longitudinal slots of the mandrel. Further, the interior and exterior surfaces of the separator ribs must be precision machined to produce surfaces that conform to the desired shape of the outer cooling jacket and inner nozzle liner. Finally, such a method also requires that the separation ribs be joined to both the outer cooling jacket and the inner nozzle liner. As a result, such a nozzle is both complex and expensive to manufacture.
Thus, there exists a need for manufacturing a channeled wall thrust nozzle, wherein cooling channels can be constructed with relatively high precision while avoiding costly and complex machining steps.
In accordance with the present invention, a method for manufacturing a channeled wall thrust nozzle is provided. The channeled wall thrust nozzle includes a thrust nozzle liner, a jacket, and at least one channel separation rib. The composite cooling jacket, channel separation rib, and thrust nozzle liner are situated so that the separation rib is positioned between the jacket and the nozzle liner, thereby forming a gap between the jacket and the nozzle liner. The gap allows the passage of a cooling fluid between the jacket and thrust nozzle liner in a heat exchange relationship with combustible gases flowing along the inner surface of the thrust nozzle liner.
The method of manufacture includes the steps of integrally forming at least one rib on either a thrust nozzle liner or an outer mold. The mold is placed around the thrust nozzle liner to form a gap between the thrust nozzle liner and the mold. The gap is filled with a removable casting material. The method also includes the steps of wrapping the thrust nozzle liner with a composite material, and removing the removable casting material to form at least one channel extending the length of the nozzle liner.
A thrust nozzle formed in accordance with the method of the present invention has several advantages over currently available methods. First, because the method of the present invention combines several manufacturing steps, it is economical. Because the separation ribs may be formed on either the thrust nozzle liner or mold, it is more versatile. Furthermore, because the method does not require machining after the formation of the cooling channels, it is less costly to manufacture. Also, such a nozzle is lighter in weight when compared to existing nozzles. Finally, a thrust nozzle formed in accordance with the present invention has fewer machined parts and, therefore, results in a further reduction in cost to manufacturer. Thus, a thrust nozzle formed in accordance with the method of the present invention is simpler to manufacture and, therefore, is economical to produce.